CA1266967A - Contact-free measuring apparatus having an f-h- corrected objective and method for using the same - Google Patents
Contact-free measuring apparatus having an f-h- corrected objective and method for using the sameInfo
- Publication number
- CA1266967A CA1266967A CA000514194A CA514194A CA1266967A CA 1266967 A CA1266967 A CA 1266967A CA 000514194 A CA000514194 A CA 000514194A CA 514194 A CA514194 A CA 514194A CA 1266967 A CA1266967 A CA 1266967A
- Authority
- CA
- Canada
- Prior art keywords
- light beam
- catadioptric
- deflecting
- elements
- optical
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000000034 method Methods 0.000 title abstract description 3
- 230000003287 optical effect Effects 0.000 claims abstract description 42
- 230000005499 meniscus Effects 0.000 claims abstract description 19
- 238000005259 measurement Methods 0.000 claims abstract description 12
- 238000000576 coating method Methods 0.000 claims description 10
- 239000011248 coating agent Substances 0.000 claims description 8
- CPBQJMYROZQQJC-UHFFFAOYSA-N helium neon Chemical compound [He].[Ne] CPBQJMYROZQQJC-UHFFFAOYSA-N 0.000 claims description 2
- 230000001131 transforming effect Effects 0.000 claims 2
- 238000010276 construction Methods 0.000 abstract description 4
- 239000000463 material Substances 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 2
- 241001163743 Perlodes Species 0.000 description 1
- 230000002844 continuous effect Effects 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 238000005137 deposition process Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/10—Scanning systems
- G02B26/12—Scanning systems using multifaceted mirrors
- G02B26/125—Details of the optical system between the polygonal mirror and the image plane
- G02B26/126—Details of the optical system between the polygonal mirror and the image plane including curved mirrors
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
- G02B19/0004—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed
- G02B19/0028—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed refractive and reflective surfaces, e.g. non-imaging catadioptric systems
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
- G02B19/0033—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use
- G02B19/0047—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a light source
Abstract
TITLE: CONTACT FREE MEASURING APPARATUS HAVING AN F-THETA-CORRECTED OBJECTIVE AND METHOD FOR USING THE SAME
ABSTRACT OF THE DISCLOSURE
An apparatus for the non-contacting measurement of rod shaped objects contains a telecentric, F-thetacorrected objective which comprises two catadioptric elements.
The first catadioptric element is a Mangin mirror and the second catadioptric element is a plane plate mirror-coated at the front, while a third optical element is a meniscus lens . The use of catadioptric elements permits a simplified and inexpensive form of construction which is also compact, as a result of which objects with large dimensions can be measureed quickly and accurately.
Such an apparatus serves, in particular, for the continuous control of the production of filament-shaped objects.
ABSTRACT OF THE DISCLOSURE
An apparatus for the non-contacting measurement of rod shaped objects contains a telecentric, F-thetacorrected objective which comprises two catadioptric elements.
The first catadioptric element is a Mangin mirror and the second catadioptric element is a plane plate mirror-coated at the front, while a third optical element is a meniscus lens . The use of catadioptric elements permits a simplified and inexpensive form of construction which is also compact, as a result of which objects with large dimensions can be measureed quickly and accurately.
Such an apparatus serves, in particular, for the continuous control of the production of filament-shaped objects.
Description
g~
BACKGROUND OF THE IN~ENTION
There are various apparatuses and methods for the noncontacting measurement and control of objects, for example of objects in the form of threads, wire, rods or tubes, wherein, as a rule, a modulated beam of light, generally a laser beam, is guided over the object and focussed on a photodetector, the shading t.ime recorded by the photodetector being, under certain conditions, a measure of the dimension of the object to be measured. Bringing about as linear a function as possible between the dimension to be measured and the shading time can be achieved in various ways, including the use of a suitable objective. In this case, with increasing measuring speed and increasing size of the object to be measured, ever greater demands are made on the measuring system and on the optlcal system. An objective which can be used For such measuring purposes is a telecentr:ic F-theta-corrected objective. This means that the emergent central ray oF the laser .beam lies parallel to the optical ax:is for all angles of def.luction during the scanning and that thero is a linear relat:Lonship bctwer~n this anrJl0 of deFlection for tho entering beam and the linear height in the imag~ space. Known tel.ecentric systems have the disadvantage, however, that the costs of the abjective rise very steeply on enlargement of the field of .
'~
measurement and it is therefore the objeet of the present invention to provide a measuring apparatus having a -telecentric, F-theta-corrected objective which can be produced economically and permits rapid and accurate measuring and monitoring.
SllMMARY OF THE INVENTION
The present invention accordingly provides an apparatus for contact-free measuring, comprising a -teleeentri.c, F--theta-corrected objective, wherein the objeetive eomprises eatadioptrie elements.
~ n accordance with a particular embodiment of the inventi.on, an appara-tus for eon-taet-free measuremen-t of an objeet by means of a teleeentrie li.ght beam seanni.ng the objeet comprises a light source for emit-ting a li.gh-t beam. Means are provided for def:Leeting this light beam with an angular veloeity. Optieal means having an optieal axis for transformi.ng the deflected ligh-t beam into the teleeentri.c seanning ligh-t beam substantially i.n the direetion of the optieal axis are p~ovLded for seanning the objeet. The optieal means eomprised of an F-theta eorreeted objeetive eompri.s.i.ng a rneniseus lens adjaeent ;the means :for de:Electi.ng the beam. The radi.i. oE eurvature oE the meniscus lens effeet a .reEraet:i.on depencli.ncJ on the angle of defleetion of the beam, and two eatad:i.opt:ri.e elements at the si-le oE the rnen.iseus lens are~ cli.sposed opposite to the means ~or cle~:Leet:i.nc3 the .L:i.ght beam. The ~:i.mensi.on o.E eaeh set eatadi.optri.c e.Lements :i.n a cli.reetion perperldi.cuLar to the~ opti.ea:l. ax.i.s exeeed the di.men.si.orl o:~ the meni.seus Lc-!ns. ~e1eet:i.ng means are provi.decl on eaeh o:E the eatad.ioptri.e elements :Eor the beam. The de.e:l.eeted l.i.cJht beam bei.ng thereby trans-formed i.nto a teleeentri.e li.cJht beam of whieh the seann:Lng veloeity i.s propor-tional -to the angular veloe:i.ty.
.~
, ,.
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- 3a -BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated by way of example in the following drawings.
Figure 1 shows, diagrammatically, an apparatus according to the invention for the contin-uous measurement of the diameter of an object in the form of a filament.
Figure 2 shows, on an enlarged scale, a section on II-II of Figure 1, .. .
9~7 Figures 3 and 4 show, diagrammatically, a second embodiment of an ob jective according to the invention in two sections and Figure 5 shows, diagrammatically, a third embodiment of objective according to the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
During the continuous measurement of objects in the form of filaments, the object traverses a region which is crossed by an optical beam, for example of a laser, the scanning plane of which is perpendicular to the direction of travel of the material and masks the beam for a period of tirne which depends on the geometry of the beam and the dimensions of the material. For an effective rneasuremer7t of the parameter in question, for example the diameter of the object, various conditions must be fulFilled:
a) the diameter oF the beam mu~t be srnall enouyh to obtain a HtOep risr3 and fall timo of the dr3tector signal, b) the scann:ing speed mu3t be high with respect to the longitudinal movemt3nt of the material and very high wikh respect to lateral movements in the scanning direction, , 3çi~
c) the beam must be perpendicular to the object before and after the shading perlod, d) the movement of the object parallel to the measuring beam must not impair the reading;
e) the shading time should be a linear functlon of the dlameter of the object, regardless of its position within the scanning period or the field of measurement.
The first three conditions can be fulfilled by a laser beam which is reflected by a polygonal mirrar which rotates at a constant speed. The conditions d) and e) are fulfilled if the objective, which projects the lassr beam onto the object of measurement, is telecentrlc ln constructlon, that is to say if the principal ray remains parallel to the axis for all scanning angles. The last condition presupposes that the objective is F-theta-corrected, that i9 to say that the height of the beam ernerging from ths objective has a linear relation~hip to th~ angl0 of the beam entering the objectivo.
If these cunditions can be fulfillecl, the measurement oF the diameter can be carried out by a simple tneasur0ment of the shading period, as a result of which an expensive digital calculation is avoided. As ~6~
initially mentioned, F-theta-corrected telecentric objectives become very expensive if the field of measurement, that is to say the maximum height of the emergent beam, is great, that is to say if the detection of objects to be measured that have relatively large dimensions is concerned. A measur.ng apparatus and, in particular, a measuring objective, which permits a simple and therefore economical form of construction is explained in more detail below.
The proposed solution amounts to using a catadioptric, telecentric, F-theta-corrected objective. The use of two reflecting surfaces makes it possible to reduce the number of elements because the elements present are traversed twice or even three times by the laser beam.
The problem i9 made additionally more difficult, however, as a result of the fact that, in contrast to conventional catadioptric objectives, no obscuring oF
the beam rnust take place.
Fi~ure :L show~ ~:iagrammat:ically, one pos~ible constructior7 of an apparatu~7 according to the invention For the cor7tinuous detoctLng of one dimension, For example the diameter, of an object, for example a filament produced continuously. A laser 1 can be seen, for example a helium neon laser, the beam 2 of which is deFlected, by a First deflecting mirror 3, through a widening optical system 4 which widens the beam of the laser to a beam of, for example, ~mm in diameter. From the widening optical system 4, thè beam reaches a second deflecting mirror 5 and from there a polygonal mirror 6 which 7 with a constant speed of rotation, deflects the laser beam in known manner at a specific frequency and at a specific angle. It is clear that neither the number and arrangement of the de-flecting mirrors nor the arrangement of the widening optical system is imperative but results from the particuIarly compact construction of the apparatus. From the revolving mirror 6, the scanniny beam passes through the objective 7 which, in the present example, consists of three elements 71, 72, 7~ and will be described more fully below with reference to Figures 3 and l~. The optical element 71 is a meniscus lens, the optical element 72 is a Mangin mirror and the optical element 7~ is a plane-parallel plate. From the lens, the beam passes to the object ~ to be moasuretl and From there throuyh a collecting lens, for oxamplt-~ a Fresnel lens 9, to a photodetector ln. Thc evaluation electronic r~ystem, known por se, whlch i9 naturally in communicatit)n w:Lth the revolv:iny mirror, will not be gone into within the scope of this invention.
Various measures can be taken to prevent the beam from bsing obscured. For example, a coating which is only par-tially re~lecting may be carried out or the optical beam may be displaced to the side of the optical axis or the reflecting elements may be tilted sligh-tly. In the objective shown in Figures 1 and 2, partially reflec,ing coatings 74 are used on the concave mirror 72 and 75 on the reflecting plate 73 and a slight tilting bo-th of -the concave mirror 72 and of the reflecting plate 73 is carried out -Eor seconds and a fe~ minu-tes respectively. Obscuring of -the beam can be avoided by the partial coating and the slight tilting of the reflecting elements. In addition, it should be noted in connection with this embodiment that the partial coating 75 on the reflec-ting plate is disposed on the rear face of this pla-te as seen ~rom the revolving-mirror. In this arrangement, the optical elements are mounted individually and secured by means of suitable holding means 76 on an adjustable pla-te 78 which is held on the base plate 77 of a housing 11 comprising the whole.opt:ical arrangement.
A preferred ernbodiment of a telecentric, E'-theta-corrected objective is shown ln Figure 3.
The optical elemen-ts of this objective are mounted, .in conventiona:L manner, in a centred mount and the incoming bearn is of~set and bent at an angle in relation to the opt:ical axis of the ob~ective :in orcler to obtain a .scann:ing reg.i.on :Erec-! of obscura-t:Lon. 'l'he revolving mirror 6, the first optical element, the meniscus lens 121, the second optical optical Plement, the Mangin mirror 122, and the third optical element, the plane plate 123, can be seen. The meniscus lens 121 has a first refracting surface with radius Rl and a second refracting surface with radius R2. The Mangin mirror has a first reflecting surface with radius R3 and a second surface with radius R4, ~hile in this embodiment, the first surface Pl of the plane mirror 123 is provided with a reflecting layer 124. The reflecting layer 124 only extends over a portion of the plane plate. S:imilarly, the first surface of the Mangin mirror, with radius R3, is not completely provided with a reflecting layer 125. As can be seen from Figure 4, the reflecting layers 124 and 125, viewed perpendicular to the plane of Figure 3, extend over half of each of the two surfaces in question. The various distances and thicknesses wh:ich ars important for the calculation of the el2ments of the objective are g:iven by T0, Tl, r2 ~ T3 and T4. The thicknoss of the plane plat0 :l23 plays no part in the present example. rhe path of rays c~n easily be seen from fiyure 3.
The beam of light, off~et and inclin0d in relation to the optical axis of the objective, for example by a deflecting mirror (5 in Figure 1), passes from the ~26~9Çj~7 revolving mirror through the meniscus correction element, passes through the transmissive region oF the Mangin mirror and is reflected by the reflecting layer 124 on the surface Pl of the plane plate 123, reaches the reflecting surface 125 with radius R3 through the Mangin mirror and is projected through the Mangin mirror onto and through the plane plate 123 and leaves the objective as a telecentric, F-theta-corrected beam, to fall on the object to be measured. In the following Tables 1 and 2, a range for the decisive values -For the calculation are given, within which an F-theta-corrected beam can be achieved which has the necessary characteristics to be able to determine the required dimension of the object to be measured, quickly and with 9reat accuracy. The precise values then depend, int0r alia, on the glass used.
Table _l (construction clata) Radius of Thickness orReFractive Radius curvature _spacinn index aperture Entrance .0087 0.20<TO~O.Z75 0.150~Rl<~0.105 .0708 0.032<Tl<0.040 1.48<nl<1.55 -0.185<R2<-0.155 .0818 9~
Radius of Thickness or Refractive Radius curvature spacinq index aperture 0.005<T2<0.008 1.40<R3*<1.90 .0897 0.04<T~<0.06 1.48<n3<1.55 1.05<R4<1.50 .0981 0.25<T4<0.35 Pl**plane .1785 Exit .2771 *Mangin mirror surface, transmissive for the first entry of the beam ** second rnirror, reflecting for the First incidence of the beam.
The unit of length iY the focal length of the objective.
Table 2 (optical data) Wavelength oF tho light 0.6328 ~m Relative aperture l-/115 F:ield angle ~/-15 degreos Scann:Lng heicJht ~ 0.261926 20 Focal length 1.000 OfFset distance entry beam 0.021~27 Type of cJlass used 517642 Theoretical error in linearity ~/- 2.043 . 10 Within the scope of such an objective, it is also . ,.,., ~, /
~66~36~
possible to use two meniscus lenses instead of one meniscus lens with a rela-tively great curvature.
In Figure 5, a simpler objective is depicted which is likewise telecentric, F-theta-corrected and catadioptric. The lens 13 is composed uf a meniscus lens 131, a face-coated mirror 132 and a plane plate 133 which is likewise face-caated. As in the preceding example, the coatings 134 on the mirrors 132 and 135 on the plane plate 133 are only partially effected in order to avoid obscuring the beam. ~ere, too, either the coated mirror 132 and the plane plate 133 can be inclined in relation to the ray path or the elements can be l<ept centred in conventional manner and the beam be taken through the objective offset and inclined.
The values For this objective vary within the scope of Table 1 with the exception of the values for the reflecting mirror 132 because the rays only travel onc~
through it. The values For R5 may vary between 6.5 and .5 and the values of R6 betweon 1.5 and 2.00.
It is also pos~lble1 however, within the scope of this lnvont:ion, to u~e more rn~niscua lens~s instead oF one or two and to use a plate or mirror which i8 likewi90 curved instead of a plane plate. As can be seen from Figur0s 1, 3 and 5, the plane plate or curved mirror can be provided with a reflecting coating on the front i7 or rear face. If a curved mirror is used instead of a plane plate and this is mirror-coated on the second face, the corresponding values for the other optical elements are naturally altered. The coating of the mirrors is effected by conventional vapour-deposition processes or by chemical means. As can be seen from Figures 2 and 4, the mirror element and the plane plate are rectangular strips but they may, of course, also be circular mirror or plates. It is likewise also possible to make the meniscus lens other than round.
Whereas in the above i-t is exclusively a question of spherical or plane elements, it is also possible to construct an objective with cylindrical optical elements so as to obtain an exit beam which lies substantially in one plane which also leads to advantages in the evaluation.
,
BACKGROUND OF THE IN~ENTION
There are various apparatuses and methods for the noncontacting measurement and control of objects, for example of objects in the form of threads, wire, rods or tubes, wherein, as a rule, a modulated beam of light, generally a laser beam, is guided over the object and focussed on a photodetector, the shading t.ime recorded by the photodetector being, under certain conditions, a measure of the dimension of the object to be measured. Bringing about as linear a function as possible between the dimension to be measured and the shading time can be achieved in various ways, including the use of a suitable objective. In this case, with increasing measuring speed and increasing size of the object to be measured, ever greater demands are made on the measuring system and on the optlcal system. An objective which can be used For such measuring purposes is a telecentr:ic F-theta-corrected objective. This means that the emergent central ray oF the laser .beam lies parallel to the optical ax:is for all angles of def.luction during the scanning and that thero is a linear relat:Lonship bctwer~n this anrJl0 of deFlection for tho entering beam and the linear height in the imag~ space. Known tel.ecentric systems have the disadvantage, however, that the costs of the abjective rise very steeply on enlargement of the field of .
'~
measurement and it is therefore the objeet of the present invention to provide a measuring apparatus having a -telecentric, F-theta-corrected objective which can be produced economically and permits rapid and accurate measuring and monitoring.
SllMMARY OF THE INVENTION
The present invention accordingly provides an apparatus for contact-free measuring, comprising a -teleeentri.c, F--theta-corrected objective, wherein the objeetive eomprises eatadioptrie elements.
~ n accordance with a particular embodiment of the inventi.on, an appara-tus for eon-taet-free measuremen-t of an objeet by means of a teleeentrie li.ght beam seanni.ng the objeet comprises a light source for emit-ting a li.gh-t beam. Means are provided for def:Leeting this light beam with an angular veloeity. Optieal means having an optieal axis for transformi.ng the deflected ligh-t beam into the teleeentri.c seanning ligh-t beam substantially i.n the direetion of the optieal axis are p~ovLded for seanning the objeet. The optieal means eomprised of an F-theta eorreeted objeetive eompri.s.i.ng a rneniseus lens adjaeent ;the means :for de:Electi.ng the beam. The radi.i. oE eurvature oE the meniscus lens effeet a .reEraet:i.on depencli.ncJ on the angle of defleetion of the beam, and two eatad:i.opt:ri.e elements at the si-le oE the rnen.iseus lens are~ cli.sposed opposite to the means ~or cle~:Leet:i.nc3 the .L:i.ght beam. The ~:i.mensi.on o.E eaeh set eatadi.optri.c e.Lements :i.n a cli.reetion perperldi.cuLar to the~ opti.ea:l. ax.i.s exeeed the di.men.si.orl o:~ the meni.seus Lc-!ns. ~e1eet:i.ng means are provi.decl on eaeh o:E the eatad.ioptri.e elements :Eor the beam. The de.e:l.eeted l.i.cJht beam bei.ng thereby trans-formed i.nto a teleeentri.e li.cJht beam of whieh the seann:Lng veloeity i.s propor-tional -to the angular veloe:i.ty.
.~
, ,.
~L2~6~
- 3a -BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated by way of example in the following drawings.
Figure 1 shows, diagrammatically, an apparatus according to the invention for the contin-uous measurement of the diameter of an object in the form of a filament.
Figure 2 shows, on an enlarged scale, a section on II-II of Figure 1, .. .
9~7 Figures 3 and 4 show, diagrammatically, a second embodiment of an ob jective according to the invention in two sections and Figure 5 shows, diagrammatically, a third embodiment of objective according to the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
During the continuous measurement of objects in the form of filaments, the object traverses a region which is crossed by an optical beam, for example of a laser, the scanning plane of which is perpendicular to the direction of travel of the material and masks the beam for a period of tirne which depends on the geometry of the beam and the dimensions of the material. For an effective rneasuremer7t of the parameter in question, for example the diameter of the object, various conditions must be fulFilled:
a) the diameter oF the beam mu~t be srnall enouyh to obtain a HtOep risr3 and fall timo of the dr3tector signal, b) the scann:ing speed mu3t be high with respect to the longitudinal movemt3nt of the material and very high wikh respect to lateral movements in the scanning direction, , 3çi~
c) the beam must be perpendicular to the object before and after the shading perlod, d) the movement of the object parallel to the measuring beam must not impair the reading;
e) the shading time should be a linear functlon of the dlameter of the object, regardless of its position within the scanning period or the field of measurement.
The first three conditions can be fulfilled by a laser beam which is reflected by a polygonal mirrar which rotates at a constant speed. The conditions d) and e) are fulfilled if the objective, which projects the lassr beam onto the object of measurement, is telecentrlc ln constructlon, that is to say if the principal ray remains parallel to the axis for all scanning angles. The last condition presupposes that the objective is F-theta-corrected, that i9 to say that the height of the beam ernerging from ths objective has a linear relation~hip to th~ angl0 of the beam entering the objectivo.
If these cunditions can be fulfillecl, the measurement oF the diameter can be carried out by a simple tneasur0ment of the shading period, as a result of which an expensive digital calculation is avoided. As ~6~
initially mentioned, F-theta-corrected telecentric objectives become very expensive if the field of measurement, that is to say the maximum height of the emergent beam, is great, that is to say if the detection of objects to be measured that have relatively large dimensions is concerned. A measur.ng apparatus and, in particular, a measuring objective, which permits a simple and therefore economical form of construction is explained in more detail below.
The proposed solution amounts to using a catadioptric, telecentric, F-theta-corrected objective. The use of two reflecting surfaces makes it possible to reduce the number of elements because the elements present are traversed twice or even three times by the laser beam.
The problem i9 made additionally more difficult, however, as a result of the fact that, in contrast to conventional catadioptric objectives, no obscuring oF
the beam rnust take place.
Fi~ure :L show~ ~:iagrammat:ically, one pos~ible constructior7 of an apparatu~7 according to the invention For the cor7tinuous detoctLng of one dimension, For example the diameter, of an object, for example a filament produced continuously. A laser 1 can be seen, for example a helium neon laser, the beam 2 of which is deFlected, by a First deflecting mirror 3, through a widening optical system 4 which widens the beam of the laser to a beam of, for example, ~mm in diameter. From the widening optical system 4, thè beam reaches a second deflecting mirror 5 and from there a polygonal mirror 6 which 7 with a constant speed of rotation, deflects the laser beam in known manner at a specific frequency and at a specific angle. It is clear that neither the number and arrangement of the de-flecting mirrors nor the arrangement of the widening optical system is imperative but results from the particuIarly compact construction of the apparatus. From the revolving mirror 6, the scanniny beam passes through the objective 7 which, in the present example, consists of three elements 71, 72, 7~ and will be described more fully below with reference to Figures 3 and l~. The optical element 71 is a meniscus lens, the optical element 72 is a Mangin mirror and the optical element 7~ is a plane-parallel plate. From the lens, the beam passes to the object ~ to be moasuretl and From there throuyh a collecting lens, for oxamplt-~ a Fresnel lens 9, to a photodetector ln. Thc evaluation electronic r~ystem, known por se, whlch i9 naturally in communicatit)n w:Lth the revolv:iny mirror, will not be gone into within the scope of this invention.
Various measures can be taken to prevent the beam from bsing obscured. For example, a coating which is only par-tially re~lecting may be carried out or the optical beam may be displaced to the side of the optical axis or the reflecting elements may be tilted sligh-tly. In the objective shown in Figures 1 and 2, partially reflec,ing coatings 74 are used on the concave mirror 72 and 75 on the reflecting plate 73 and a slight tilting bo-th of -the concave mirror 72 and of the reflecting plate 73 is carried out -Eor seconds and a fe~ minu-tes respectively. Obscuring of -the beam can be avoided by the partial coating and the slight tilting of the reflecting elements. In addition, it should be noted in connection with this embodiment that the partial coating 75 on the reflec-ting plate is disposed on the rear face of this pla-te as seen ~rom the revolving-mirror. In this arrangement, the optical elements are mounted individually and secured by means of suitable holding means 76 on an adjustable pla-te 78 which is held on the base plate 77 of a housing 11 comprising the whole.opt:ical arrangement.
A preferred ernbodiment of a telecentric, E'-theta-corrected objective is shown ln Figure 3.
The optical elemen-ts of this objective are mounted, .in conventiona:L manner, in a centred mount and the incoming bearn is of~set and bent at an angle in relation to the opt:ical axis of the ob~ective :in orcler to obtain a .scann:ing reg.i.on :Erec-! of obscura-t:Lon. 'l'he revolving mirror 6, the first optical element, the meniscus lens 121, the second optical optical Plement, the Mangin mirror 122, and the third optical element, the plane plate 123, can be seen. The meniscus lens 121 has a first refracting surface with radius Rl and a second refracting surface with radius R2. The Mangin mirror has a first reflecting surface with radius R3 and a second surface with radius R4, ~hile in this embodiment, the first surface Pl of the plane mirror 123 is provided with a reflecting layer 124. The reflecting layer 124 only extends over a portion of the plane plate. S:imilarly, the first surface of the Mangin mirror, with radius R3, is not completely provided with a reflecting layer 125. As can be seen from Figure 4, the reflecting layers 124 and 125, viewed perpendicular to the plane of Figure 3, extend over half of each of the two surfaces in question. The various distances and thicknesses wh:ich ars important for the calculation of the el2ments of the objective are g:iven by T0, Tl, r2 ~ T3 and T4. The thicknoss of the plane plat0 :l23 plays no part in the present example. rhe path of rays c~n easily be seen from fiyure 3.
The beam of light, off~et and inclin0d in relation to the optical axis of the objective, for example by a deflecting mirror (5 in Figure 1), passes from the ~26~9Çj~7 revolving mirror through the meniscus correction element, passes through the transmissive region oF the Mangin mirror and is reflected by the reflecting layer 124 on the surface Pl of the plane plate 123, reaches the reflecting surface 125 with radius R3 through the Mangin mirror and is projected through the Mangin mirror onto and through the plane plate 123 and leaves the objective as a telecentric, F-theta-corrected beam, to fall on the object to be measured. In the following Tables 1 and 2, a range for the decisive values -For the calculation are given, within which an F-theta-corrected beam can be achieved which has the necessary characteristics to be able to determine the required dimension of the object to be measured, quickly and with 9reat accuracy. The precise values then depend, int0r alia, on the glass used.
Table _l (construction clata) Radius of Thickness orReFractive Radius curvature _spacinn index aperture Entrance .0087 0.20<TO~O.Z75 0.150~Rl<~0.105 .0708 0.032<Tl<0.040 1.48<nl<1.55 -0.185<R2<-0.155 .0818 9~
Radius of Thickness or Refractive Radius curvature spacinq index aperture 0.005<T2<0.008 1.40<R3*<1.90 .0897 0.04<T~<0.06 1.48<n3<1.55 1.05<R4<1.50 .0981 0.25<T4<0.35 Pl**plane .1785 Exit .2771 *Mangin mirror surface, transmissive for the first entry of the beam ** second rnirror, reflecting for the First incidence of the beam.
The unit of length iY the focal length of the objective.
Table 2 (optical data) Wavelength oF tho light 0.6328 ~m Relative aperture l-/115 F:ield angle ~/-15 degreos Scann:Lng heicJht ~ 0.261926 20 Focal length 1.000 OfFset distance entry beam 0.021~27 Type of cJlass used 517642 Theoretical error in linearity ~/- 2.043 . 10 Within the scope of such an objective, it is also . ,.,., ~, /
~66~36~
possible to use two meniscus lenses instead of one meniscus lens with a rela-tively great curvature.
In Figure 5, a simpler objective is depicted which is likewise telecentric, F-theta-corrected and catadioptric. The lens 13 is composed uf a meniscus lens 131, a face-coated mirror 132 and a plane plate 133 which is likewise face-caated. As in the preceding example, the coatings 134 on the mirrors 132 and 135 on the plane plate 133 are only partially effected in order to avoid obscuring the beam. ~ere, too, either the coated mirror 132 and the plane plate 133 can be inclined in relation to the ray path or the elements can be l<ept centred in conventional manner and the beam be taken through the objective offset and inclined.
The values For this objective vary within the scope of Table 1 with the exception of the values for the reflecting mirror 132 because the rays only travel onc~
through it. The values For R5 may vary between 6.5 and .5 and the values of R6 betweon 1.5 and 2.00.
It is also pos~lble1 however, within the scope of this lnvont:ion, to u~e more rn~niscua lens~s instead oF one or two and to use a plate or mirror which i8 likewi90 curved instead of a plane plate. As can be seen from Figur0s 1, 3 and 5, the plane plate or curved mirror can be provided with a reflecting coating on the front i7 or rear face. If a curved mirror is used instead of a plane plate and this is mirror-coated on the second face, the corresponding values for the other optical elements are naturally altered. The coating of the mirrors is effected by conventional vapour-deposition processes or by chemical means. As can be seen from Figures 2 and 4, the mirror element and the plane plate are rectangular strips but they may, of course, also be circular mirror or plates. It is likewise also possible to make the meniscus lens other than round.
Whereas in the above i-t is exclusively a question of spherical or plane elements, it is also possible to construct an objective with cylindrical optical elements so as to obtain an exit beam which lies substantially in one plane which also leads to advantages in the evaluation.
,
Claims (11)
1. An apparatus for contact-free measurement of an object by means of a telecentric light beam scanning said object, comprising a light source for emitting a light beam, means for deflecting this light beam with an angular velocity, optical means having an optical axis, for transforming said deflected light beam into said telecentric scanning light beam substantially in the direction of said optical axis for scanning said object, said optical means comprising an F-theta- corrected objective comprising a meniscus lens adjacent said means for deflecting said beam, the radii of curvature of said meniscus lens effecting a refraction depending on the angle of deflection of said beam, and two cata-dioptric elements at the side of said meniscus lens opposite to said means for deflecting the light beam, the dimension of each of said catadioptric elements in a direction perpendicular to the optical axis exceeding the dimension of said meniscus lens, reflecting means on each of said catadioptric elements for said beam, said deflected light beam being thereby transformed into a telecentric light beam of which the scanning velocity is proportional to said angular velocity.
2. An apparatus as claimed in claim 1, wherein one of the catadioptric elements is a spherical mirror.
3. An apparatus as claimed in claim 1, said optical means comprising cylindrical optical elements.
4. An apparatus as claimed in claim 1, wherein the catadioptric elements are partially covered with a reflecting coating.
5. An apparatus as claimed in claim 4, wherein the catadioptric elements are tilted with respect to the optical axis in order, together with the reflect-ing coating, to avoid obscuring of the beam emerging from the objective.
6. An apparatus as claimed in claim 4, wherein the beam is offset and inclined in relation to the optical axis of the objective in order, together with the reflecting coating, to avoid obscuring of the beam emerging from the objective.
7. An apparatus as claimed in claim 1, wherein the optical elements are of rectangular cross section.
8. An apparatus as claimed in claim 1, wherein said light source comprises a helium-neon laser, two adjustable deflecting mirrors, a widening optical system disposed between the two deflecting mirrors and a revolving mirror from which the beam is deflected and reaches the objective, all parts being disposed in a housing
9. An apparatus for contact-free measurement of an object by means of a telecentric light beam scanning said object, comprising a light source for emitting a light beam, means for deflecting this light beam with an angular velocity, optical means having an optical axis, for transforming said deflected light beam into said telecentric scanning light beam substantially in the direction of said optical axis for scanning said object, said optical means comprising an F-theta-corrected objective comprising a meniscus lens adjacent said means for deflecting said beam, a first catadioptric element at the side of said meniscus lens opposite to said means for deflecting the light beam, said first cata-dioptric element having curved surfaces, and a second catadioptric element having plane surfaces at the outlet of said optical means, at least one dimension of each of said catadioptric elements in a direction perpendicular to said optical axis exceeding the dimension of said meniscus lens, and each of said catadioptric elements having reflecting means for said beam said deflected light beam being thereby transformed into a telecentric light beam of which the scanning velocity is proportional to said angular velocity.
10. An apparatus according to claim 9, wherein said means for deflecting the light beam, said meniscus lens, said first catadioptric element and said second catadioptric element are spaced from each other by distances T0, T2 and T4 respectively, said meniscus lens has a thickness of T1 and radii of curvature R1 and R2, said first catadioptric element has a thickness T3 and radii of curvature R3 and R4, said distances and thicknesses being measured in said optical axis, these parameters and the refractive index being as follows:
11. An apparatus for contact-free measurement of an object by means of a light beam scanning said object, comprising a light source for emitting a light beam, means for deflecting this light beam substantially in the direction of said optical axis for scanning said object, said optical means compris-ing an F-theta-corrected objective comprising a lens adjacent said means for deflecting said beam, and two catadioptric elements at the side of said lens opposite to said means for deflecting the light beam, the dimension of said catadioptric elements in a direction perpendicular to the optical axis exceeding the dimension of said lens, said deflected light beam being thereby transformed into a telecentric light beam of which the scanning velocity is proportional to said angular velocity, said catadioptric elements being strip-shaped and extending substantially in said deflecting plane, each of said catadioptric elements having an elongated mirror extending along one side thereof and a light transmitting zone extending along the other side thereof, said beam being transmitted through each of said elements at said light-transmitting zone and reflected by said mirror, said deflected beam and said telecentric beam being in parallel planes adjacent each other.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH03'219/85-7 | 1985-07-24 | ||
| CH3219/85A CH668322A5 (en) | 1985-07-24 | 1985-07-24 | DEVICE WITH A TELECENTRIC, F-THETA-CORRECTED LENS FOR CONTACT-FREE MEASUREMENT AND USE OF THIS DEVICE. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1266967A true CA1266967A (en) | 1990-03-27 |
Family
ID=4251219
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000514194A Expired - Lifetime CA1266967A (en) | 1985-07-24 | 1986-07-18 | Contact-free measuring apparatus having an f-h- corrected objective and method for using the same |
Country Status (10)
| Country | Link |
|---|---|
| US (1) | US4792695A (en) |
| EP (1) | EP0211803B1 (en) |
| JP (1) | JP2618377B2 (en) |
| AT (1) | ATE53679T1 (en) |
| AU (1) | AU586266B2 (en) |
| CA (1) | CA1266967A (en) |
| CH (1) | CH668322A5 (en) |
| DE (1) | DE3671984D1 (en) |
| ES (1) | ES2000931A6 (en) |
| ZA (1) | ZA865424B (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU598418B2 (en) * | 1988-06-04 | 1990-06-21 | Fujitsu Limited | Optical system for detecting three-dimensional shape |
| US4987304A (en) * | 1989-09-29 | 1991-01-22 | Eastman Kodak Company | Telecentric scanning for transparent storage phosphors |
| US5134511A (en) * | 1989-12-08 | 1992-07-28 | Kabushiki Kaisha Toshiba | Optical unit for use in laser beam printer or the like |
| US5461228A (en) | 1994-04-07 | 1995-10-24 | Owens-Brockway Glass Container Inc. | Optical inspection of container dimensional parameters using a telecentric lens |
| US5610391A (en) * | 1994-08-25 | 1997-03-11 | Owens-Brockway Glass Container Inc. | Optical inspection of container finish dimensional parameters |
| NL1003530C2 (en) * | 1996-07-06 | 1998-01-12 | Philips Electronics Nv | Wide-angle scanning objective system and scanning apparatus with such an objective system. |
| US5717518A (en) | 1996-07-22 | 1998-02-10 | Kla Instruments Corporation | Broad spectrum ultraviolet catadioptric imaging system |
| US6256095B1 (en) | 2000-01-21 | 2001-07-03 | Owens-Brockway Glass Container Inc. | Container sealing surface area inspection |
| US7136159B2 (en) * | 2000-09-12 | 2006-11-14 | Kla-Tencor Technologies Corporation | Excimer laser inspection system |
| DE102012107040A1 (en) * | 2012-08-01 | 2014-05-28 | Jenoptik Optical Systems Gmbh | Achromatic scanning device with monochromatic f-theta lens |
Family Cites Families (25)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE967578C (en) * | 1952-09-24 | 1957-11-21 | Erwin Sick | Photoelectric barrier |
| US3527526A (en) * | 1965-05-26 | 1970-09-08 | Ernest W Silvertooth | Catoptric image-forming system in which light is reflected twice from each surface |
| US3520586A (en) * | 1966-06-20 | 1970-07-14 | Ampex | Entrant beam optical scanner |
| US3547525A (en) * | 1967-08-31 | 1970-12-15 | Perkin Elmer Corp | Catadioptric system |
| US3667360A (en) * | 1969-04-23 | 1972-06-06 | Columbia Broadcasting Syst Inc | Optical scanning system |
| US3700310A (en) * | 1971-09-10 | 1972-10-24 | Perkin Elmer Corp | Compact catadioptric apochromat system |
| CH541140A (en) * | 1971-12-31 | 1973-08-31 | Gretag Ag | Lighting arrangement |
| US3858046A (en) * | 1973-06-25 | 1974-12-31 | Hughes Aircraft Co | Catadioptric beamsplitter system |
| US3926505A (en) * | 1974-07-22 | 1975-12-16 | Perkin Elmer Corp | All spherical solid catadioptric systems |
| GB1567604A (en) * | 1976-02-02 | 1980-05-21 | Rank Organisation Ltd | Optical system |
| DE2622113C3 (en) * | 1976-05-18 | 1982-04-08 | Erwin Sick Gmbh Optik-Elektronik, 7808 Waldkirch | Optical device for correcting the spherical aberration of a spherical concave mirror |
| US4074938A (en) * | 1976-09-27 | 1978-02-21 | Systems Research Laboratories, Inc. | Optical dimension measuring device employing an elongated focused beam |
| JPS6018045B2 (en) * | 1977-04-22 | 1985-05-08 | オリンパス光学工業株式会社 | reflective objective lens |
| US4168126A (en) * | 1977-07-05 | 1979-09-18 | Altman Associates, Inc. | Electro-optical measuring system using precision light translator |
| US4342503A (en) * | 1979-10-09 | 1982-08-03 | The Perkin-Elmer Corporation | Catadioptric telescopes |
| AT365787B (en) * | 1980-02-12 | 1982-02-10 | Eumig | CATADIOPTRIC LENS |
| JPS6053294B2 (en) * | 1980-06-20 | 1985-11-25 | 株式会社ニコン | 4-group fθ lens system |
| CH651943A5 (en) * | 1980-08-16 | 1985-10-15 | Ludvik Dr Canzek | HIGH OPENING CATADIOPTRIC LENS. |
| JPS5888716A (en) * | 1981-11-24 | 1983-05-26 | Canon Inc | Lens for equal-speed scanning having high resolving power |
| NL8105795A (en) * | 1981-12-22 | 1983-07-18 | Optische Ind De Oude Delft Nv | MIRROR-LENS. |
| SE433783B (en) * | 1982-03-03 | 1984-06-12 | Pharos Ab | OPTICAL SWEEPING DEVICE |
| US4639141A (en) * | 1982-11-12 | 1987-01-27 | Mitutoyo Mfg. Co., Ltd. | Scanning ray beam generator for optical measuring device |
| SU1142732A1 (en) * | 1983-11-29 | 1985-02-28 | Предприятие П/Я В-2080 | Device for checking linear dimensions |
| DE3505198C1 (en) * | 1985-02-15 | 1986-07-24 | Bodenseewerk Gerätetechnik GmbH, 7770 Überlingen | Device for scanning a visual field |
| JPH111402A (en) * | 1997-06-10 | 1999-01-06 | Nippon Kayaku Co Ltd | Water surface-floating agrochemical preparation |
-
1985
- 1985-07-24 CH CH3219/85A patent/CH668322A5/en not_active IP Right Cessation
-
1986
- 1986-07-14 US US06/885,874 patent/US4792695A/en not_active Expired - Lifetime
- 1986-07-15 AT AT86810316T patent/ATE53679T1/en active
- 1986-07-15 EP EP86810316A patent/EP0211803B1/en not_active Expired - Lifetime
- 1986-07-15 DE DE8686810316T patent/DE3671984D1/en not_active Expired - Lifetime
- 1986-07-18 CA CA000514194A patent/CA1266967A/en not_active Expired - Lifetime
- 1986-07-21 ZA ZA865424A patent/ZA865424B/en unknown
- 1986-07-22 JP JP61170990A patent/JP2618377B2/en not_active Expired - Lifetime
- 1986-07-22 AU AU60418/86A patent/AU586266B2/en not_active Ceased
- 1986-07-23 ES ES8600507A patent/ES2000931A6/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| ATE53679T1 (en) | 1990-06-15 |
| JPS6228707A (en) | 1987-02-06 |
| US4792695A (en) | 1988-12-20 |
| AU586266B2 (en) | 1989-07-06 |
| EP0211803A1 (en) | 1987-02-25 |
| ZA865424B (en) | 1987-03-25 |
| AU6041886A (en) | 1987-01-29 |
| ES2000931A6 (en) | 1988-04-01 |
| CH668322A5 (en) | 1988-12-15 |
| EP0211803B1 (en) | 1990-06-13 |
| DE3671984D1 (en) | 1990-07-19 |
| JP2618377B2 (en) | 1997-06-11 |
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